Answer:
Another key achievement of the Khmer Empire was its ability to build strong trade links with societies across South-East Asia. Trade in rice and fish became a key part of the Khmer Empire's economy. Use of the Mekong River allowed the Khmer to trade in regions both north and south of the empire.
The correct answer for the given question above would be the third option. The Song Dynasty as compared to the Tang Dynasty is that, the Song Dynasty was smaller than the Tang Dynasty, but lasted for a slightly longer period of time. The Song Dynasty didn't expand much, whereas, the Tang Dynasty expanded to modern borders. Hope this answer helps.
